1. Field of the Invention
This invention relates to carboxylic acid derivatives and their synthesis method and more particularly, to novel carboxylic acid derivatives represented by the following formula I via introduction of some protecting group which can be easily decomposed by acid, including their synthesis method. ##STR2##
wherein, R.sub.1 is an hydrogen atom, an alkyl group or an alkoxy group of 1 to 20 carbon atoms in a linear, branched or cyclic form; R.sub.2 is a carboxy group of 1 to 40 carbon atoms in a linear, branched or cyclic form which is unsubstituted, or substituted into a hydroxy group, an ester group and an ether group. PA1 wherein, R.sub.1 is an hydrogen atom, an alkyl group or an alkoxy group of 1 to 20 carbon atoms in a linear, branched or cylic form; R.sub.2 is a carboxy group of 1 to 40 carbon atoms in a linear, branched or cyclic form which is unsubstituted, or substituted into a hydroxy group, an ester group and an ether group. PA1 R.sub.1 --CHX.sub.2 PA1 R.sub.2 --H
2. Description of the Related Art
As an additive or active ingredient of a resist, an electronic material, carboxylic acid compounds serve to improve the etching resistance and pattern profile of the resist.
It has been reported that one example of such carboxylic acid derivatives introducing t-butyl group as a protecting group includes t-butyl deoxycholate or t-butyl lithocholate (Proc. SPIE 3049, 84, 1997).
However, the resist containing such carboxylic acid derivatives has recognized some disadvantages in that the insolubility of basic aqueous solution in a unexposed area cannot be overcome and the resist cannot be easily decomposed by acid.
In consequence, when the resist is developed for the final patterning using developer, the unexposed resist area is etched and this may lead to a poor pattern profile.